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Which of the following compounds, on treatment with dilute H2SO4, gives the major product P — a tertiary alcohol in which a cyclohexane ring is attached to a carbon bearing -OH, -CH3, and -CH2CH3 groups?

1. Cyclohexyl-substituted alkene: cyclohexane-CH(CH3)-CH=CH2
2. Cyclohexene ring bearing an isopropyl substituent at the allylic carbon (double bond in the ring)
3. Cyclohexyl-substituted secondary alcohol: cyclohexane-CH(CH3)-CH(OH)-CH3
4. Cyclohexene ring bearing the same isopropyl substituent but with the double bond at a different position in the ring

Correct answer: Cyclohexyl-substituted alkene: cyclohexane-CH(CH3)-CH=CH2

Solution

Acid-catalysed hydration of cyclohexane-CH(CH3)-CH=CH2 (Markovnikov): H+ adds to the terminal CH2, giving a carbocation at the internal carbon which already bears CH3 and cyclohexyl groups, then OH- adds to give the tertiary alcohol C(OH)(CH3)(CH2CH3) attached to cyclohexane.

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